<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script type="text/javascript" src="calc.js"></script>
</head>
<body>
    <b>DATA1:</b><input type="text" id="data1">
    <br>
    <b>DATA2:</b><input type="text" id="data2">
    <br>
    <b>result:</b><input type="text" id="ret">
    <br>
    <input type="button" value="ADD" onclick="calc_fun(1);">
    <input type="button" value="SUB" onclick="calc_fun(0);">
    
</body>
</html>